Buggy code:
public class ScalaWriter extends AbstractCodeWriter < ScalaWriter > { private static final Set < String > PRIMITIVE_TYPES = new HashSet < String > ( Arrays . asList ( "boolean" , "byte" , "char" , "int" , "long" , "short" , "double" , "float" ) ) ; private static final String DEF = "def<seq2seq4repair_space>" ; private static final String EXTENDS = "<seq2seq4repair_space>extends<seq2seq4repair_space>" ; private static final String WITH = "<seq2seq4repair_space>with<seq2seq4repair_space>" ; private static final String IMPORT = "import<seq2seq4repair_space>" ; private static final String IMPORT_STATIC = "import<seq2seq4repair_space>" ; private static final String PACKAGE = "package<seq2seq4repair_space>" ; private static final String PRIVATE = "private<seq2seq4repair_space>" ; private static final String PRIVATE_VAL = "private<seq2seq4repair_space>val<seq2seq4repair_space>" ; private static final String PROTECTED = "protected<seq2seq4repair_space>" ; private static final String PROTECTED_VAL = "protected<seq2seq4repair_space>val<seq2seq4repair_space>" ; private static final String PUBLIC = "public<seq2seq4repair_space>" ; private static final String PUBLIC_CLASS = "class<seq2seq4repair_space>" ; private static final String PUBLIC_OBJECT = "object<seq2seq4repair_space>" ; private static final String CASE_CLASS = "case<seq2seq4repair_space>class<seq2seq4repair_space>" ; private static final String VAR = "var<seq2seq4repair_space>" ; private static final String VAL = "val<seq2seq4repair_space>" ; private static final String THIS = "this" ; private static final String TRAIT = "trait<seq2seq4repair_space>" ; private final Set < String > classes = new HashSet < String > ( ) ; private final Set < String > packages = new HashSet < String > ( ) ; private Type type ; private final boolean compact ; public ScalaWriter ( Appendable appendable ) { } public ScalaWriter ( Appendable appendable , boolean compact ) { } @ Override public ScalaWriter annotation ( Annotation annotation ) throws IOException { } @ Override public ScalaWriter annotation ( Class < ? extends Annotation > annotation ) throws IOException { } @ SuppressWarnings ( "unchecked" ) private void annotationConstant ( Object value ) throws IOException { } private ScalaWriter appendType ( Class < ? > type ) throws IOException { } public ScalaWriter beginObject ( String header ) throws IOException { } public ScalaWriter beginClass ( String header ) throws IOException { } @ Override public ScalaWriter beginClass ( Type type ) throws IOException { } @ Override public ScalaWriter beginClass ( Type type , Type superClass , Type ... interfaces ) throws IOException { } @ Override public < T > ScalaWriter beginConstructor ( Collection < T > parameters , Function < T , Parameter > transformer ) throws IOException { } @ Override public ScalaWriter beginConstructor ( Parameter ... params ) throws IOException { } @ Override public ScalaWriter beginInterface ( Type type , Type ... interfaces ) throws IOException { } private ScalaWriter beginMethod ( String modifiers , Type returnType , String methodName , Parameter ... args ) throws IOException { if ( returnType . equals ( VOID ) ) { beginLine ( modifiers , escape ( methodName ) ) . params ( args ) . append ( "<seq2seq4repair_space>{" ) . nl ( ) ; } else { <START_BUG> beginLine ( modifiers , escape ( methodName ) ) . params ( args ) . append ( ":<seq2seq4repair_space>" ) . append ( getGenericName ( true , returnType ) ) . append ( "<seq2seq4repair_space>{" ) . nl ( ) ; <END_BUG> } return goIn ( ) ; } @ Override public < T > ScalaWriter beginPublicMethod ( Type returnType , String methodName , Collection < T > parameters , Function < T , Parameter > transformer ) throws IOException { } @ Override public ScalaWriter beginPublicMethod ( Type returnType , String methodName , Parameter ... args ) throws IOException { } @ Override public < T > ScalaWriter beginStaticMethod ( Type returnType , String methodName , Collection < T > parameters , Function < T , Parameter > transformer ) throws IOException { } @ Override public ScalaWriter beginStaticMethod ( Type returnType , String methodName , Parameter ... args ) throws IOException { } public ScalaWriter caseClass ( String header , Parameter ... parameters ) throws IOException { } @ Override public ScalaWriter end ( ) throws IOException { } public ScalaWriter field ( Type type , String name ) throws IOException { } private ScalaWriter field ( String modifier , Type type , String name ) throws IOException { } private ScalaWriter field ( String modifier , Type type , String name , String value ) throws IOException { } @ Override public String getClassConstant ( String className ) { } @ Override public String getGenericName ( boolean asArgType , Type type ) { } @ Override public String getRawName ( Type type ) { } @ Override public ScalaWriter imports ( Class < ? > ... imports ) throws IOException { } @ Override public ScalaWriter imports ( Package ... imports ) throws IOException { } @ Override public ScalaWriter importClasses ( String ... imports ) throws IOException { } @ Override public ScalaWriter importPackages ( String ... imports ) throws IOException { } @ Override public ScalaWriter javadoc ( String ... lines ) throws IOException { } @ Override public ScalaWriter packageDecl ( String packageName ) throws IOException { } private < T > ScalaWriter params ( Collection < T > parameters , Function < T , Parameter > transformer ) throws IOException { } private ScalaWriter params ( Parameter ... params ) throws IOException { } private ScalaWriter param ( Parameter parameter ) throws IOException { } @ Override public ScalaWriter privateField ( Type type , String name ) throws IOException { } @ Override public ScalaWriter privateFinal ( Type type , String name ) throws IOException { } @ Override public ScalaWriter privateFinal ( Type type , String name , String value ) throws IOException { } @ Override public ScalaWriter privateStaticFinal ( Type type , String name , String value ) throws IOException { } @ Override public ScalaWriter protectedField ( Type type , String name ) throws IOException { } @ Override public ScalaWriter protectedFinal ( Type type , String name ) throws IOException { }

Fix:
beginLine ( modifiers , escape ( methodName ) ) . params ( args ) . append ( ":<seq2seq4repair_space>" ) . append ( getGenericName ( true , returnType ) ) . append ( "<seq2seq4repair_space>=<seq2seq4repair_space>{" ) . nl ( ) ;